1. Field of the Invention
The present invention relates to a magnetron to be used in a microwave oven.
2. Description of the Related Art
A conventional magnetron for a microwave oven comprises a choke coil 51 in a filter case 50, and has an end 51A of the choke coil 51 connected to a cathode input conductor 52 and the other end 51B of the choke coil 51 connected to a terminal 53A of a capacitor 53, and the capacitor 53 is provided on a side wall of the filter case 50 as shown in FIG. 14.
The choke coil 51 can solve the following problem. More specifically, an air-core type inductance 55 and a core type inductance 56 having a bar-shaped high frequency absorbing member (ferrite core) 57 in a winding are connected in series so that the dielectric breakdown of a winding in the choke coil 51 is burned to cause an insulation failure or the crack of the ferrite core 57 is generated (for example, JP-B-57-17344 Publication).
A magnetron for a microwave oven is greatly required to have a reduction in a size in order to maintain a large inner part of a microwave oven. In order to meet the requirement, a magnetron having a small height of the filter case 50 has been necessary. However, the magnetron for the microwave oven is to maintain a distance from the choke coil 51 to the filter case 50 which is equal to or greater than a specified value in order to satisfy safety standards. In the magnetron for the microwave oven, moreover, restrictions on a noise are severe differently from an industrial magnetron.
The magnetron serves to generate a high frequency in a space having a complicated structure. For this reason, a result of a simulation (a free space) and a result of an experiment are greatly different from each other. In other words, it is impossible to predict an influence in the case in which a size is reduced.